1. Technical Field
The present invention relates to semiconductor circuit technology, and more particularly, to a data driving impedance auto-calibration circuit and a semiconductor integrated circuit using the same.
2. Related Art
As an example of a semiconductor integrated circuit, a semiconductor memory device includes a data driver for driving data.
The driving impedance values for a data driver are designed to match a target value which may be used to define a chartable region of valid data output between the data driver and its load. This chartable region thus defines a data output characteristic of the data driver and is referred to as a “data eye” due to the shape formed by the data output characteristic when plotted. Unfortunately, the driving impedance of the data driver may vary from a target value to a different value, due to process, voltage or temperature (PVT) variations.
When the driving impedance of the data driver is changed to a different value from the target value, the data output characteristic, that is, the data eye, which defines a region of valid data, may becomeunstable.
Therefore, there is a demand for the development of technology which is capable of constantly maintaining the driving impedance of the data driver in correspondence to the PVT variation.